I normally back into my slip because it puts me in position to tend the lines when the boat first enters the slip when I am single handing, because the boat fits better in the slip that way, and because it's easier boarding from the pier. My boat is also a fin keel, and if in significant cross wind, the bow falls off uncontrollablely if I'm backing at low speed. So it's simple....back in when I can, but if cross winds prevent good control of boat, then dock bow first until wind subsides. Then, redock with the stern in when the wind permits this.

Additionally, I like to start the backing before I enter the fairway to the slip. This allows me to see what the cross wind is going to do to the boat, and I get good control of the boat backing before trying to enter the slip, and just drive in reverse between the pilings...you can normally hit it just right almost every time. Looks a little strange if you have a long fairway, and not all boats will do this, but it takes lots of frustration away for me. And if the cross wind is sufficient to blow off the bow uncontrollablely, you are away from other boats so there will never be risk of damage. And if bow does fall off too severely, simply turn around and make the temporary bow first landing where you have more control of the bow.